CYTOCHROMES P450 EXPRESSION SYSTEMS

Catalytically active cytochrome P450 enzymes have been successfully ex pressed in bacterial, yeast, and mammalian cells. A variety of express ion vectors have been used, resulting in both transient and stable exp ression. The system of choice depends on the goals of a particular pro ject. Factors such as expense, ease of use, and yields required should govern the decision whether to use bacterial, yeast, insect, or mamma lian cDNA expression. High-level expression of mammalian P450s in bact eria usually requires modifications of the amino-terminal region of th e enzyme. The Escherichia coli P450-OR fusion proteins may also come o f age for use in fermentation-production processes for the chemical in dustry. Many cytochromes P450 have been expressed in yeast, with varia ble levels of expression. Baculovirus, albeit somewhat tedious in havi ng to individualize expression conditions, can produce high levels of enzyme. The standard mammalian cell expression systems, both transient and stable, have been of tremendous value to drug metabolism and carc inogenesis research and will continue to play a role in these areas.